fix(sentry): skip "daemon not running" stop/reload errors

internal/agent/state.go

@@ -2,6 +2,8 @@ package agent
 
 import (
 	"encoding/json"
+	"errors"
+	"fmt"
 	"os"
 	"path/filepath"
 	"time"
@@ -9,6 +11,11 @@ import (
 	"github.com/torrentclaw/unarr/internal/config"
 )
 
+// ErrDaemonNotRunning is returned by callers that need a running daemon but
+// find no state file on disk. Sentinel so user-facing commands (stop/reload)
+// can wrap it and Sentry can filter it out as a non-bug.
+var ErrDaemonNotRunning = errors.New("daemon does not appear to be running (state file not found)")
+
 // DaemonState is written to disk every heartbeat for external tools to read.
 type DaemonState struct {
 	AgentID         string         `json:"agentId"`
@@ -69,17 +76,31 @@ func WriteState(state *DaemonState) {
 	os.Rename(tmp, path)
 }
 
-// ReadState reads the daemon state from disk. Returns nil if not found.
+// ReadState reads the daemon state from disk. Returns nil if not found or
+// unreadable. Use LoadState when callers need to distinguish "not running"
+// from "state file corrupted".
 func ReadState() *DaemonState {
+	state, _ := LoadState()
+	return state
+}
+
+// LoadState reads the daemon state and returns explicit errors:
+//   - ErrDaemonNotRunning when the state file does not exist
+//   - a wrapped json error when the file exists but cannot be decoded
+//     (a real bug worth reporting to Sentry)
+func LoadState() (*DaemonState, error) {
 	data, err := os.ReadFile(StateFilePath())
 	if err != nil {
-		return nil
+		if errors.Is(err, os.ErrNotExist) {
+			return nil, ErrDaemonNotRunning
+		}
+		return nil, err
 	}
 	var state DaemonState
-	if json.Unmarshal(data, &state) != nil {
-		return nil
+	if err := json.Unmarshal(data, &state); err != nil {
+		return nil, fmt.Errorf("decode daemon state %s: %w", StateFilePath(), err)
 	}
-	return &state
+	return &state, nil
 }
 
 // RemoveState deletes the state file (called on clean shutdown).

internal/agent/state_test.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"errors"
 	"os"
 	"path/filepath"
 	"testing"
@@ -104,3 +105,39 @@ func TestReadStateCorruptedJSON(t *testing.T) {
 		t.Errorf("ReadState() should return nil for corrupted JSON, got %+v", state)
 	}
 }
+
+func TestLoadStateNotFound(t *testing.T) {
+	tmpDir := t.TempDir()
+	origFn := stateFilePathFn
+	stateFilePathFn = func() string { return filepath.Join(tmpDir, "nonexistent.json") }
+	defer func() { stateFilePathFn = origFn }()
+
+	state, err := LoadState()
+	if state != nil {
+		t.Errorf("LoadState() state = %+v, want nil", state)
+	}
+	if !errors.Is(err, ErrDaemonNotRunning) {
+		t.Errorf("LoadState() err = %v, want ErrDaemonNotRunning", err)
+	}
+}
+
+func TestLoadStateCorruptedJSON(t *testing.T) {
+	tmpDir := t.TempDir()
+	origFn := stateFilePathFn
+	path := filepath.Join(tmpDir, "daemon.state.json")
+	stateFilePathFn = func() string { return path }
+	defer func() { stateFilePathFn = origFn }()
+
+	os.WriteFile(path, []byte("not valid json{{{"), 0o644)
+
+	state, err := LoadState()
+	if state != nil {
+		t.Errorf("LoadState() state = %+v, want nil", state)
+	}
+	if err == nil {
+		t.Fatal("LoadState() err = nil, want decode error")
+	}
+	if errors.Is(err, ErrDaemonNotRunning) {
+		t.Error("corrupt state must not be reported as ErrDaemonNotRunning — it would be filtered from Sentry")
+	}
+}